Due to changes in the size and quality of standing timber available for harvest, and economic pressure on the wood products industry, lignocellulosic composite materials have replaced and supplemented traditional solid sawn lumber for use in many structural applications. These lignocellulosic composites are formed from small pieces of cellulosic material that are bonded with an adhesive or binder. In general, the small pieces of cellulosic material are produced by fragmenting solid wood into strands, fibers or chips. A wood adhesive is then added to the fragmented wood material. The resulting mixture is then typically subjected to heat and pressure, which forms a composite material. The adhesive is typically the major non-woody component of the composite.
Currently, most wood composites use a phenol-formaldehyde (PF) or urea-formaldehyde (UF) wood adhesive. These adhesive materials suffer from two major drawbacks. First, both adhesives release volatile organic compounds (VOC) during their manufacture and during their use. Released VOC include chemicals that are thought to be hazardous to human health, such as formaldehyde, which is a suspected carcinogen. Increasing concern about the effect of emissive VOC, particularly formaldehyde, on human health has prompted the development of more benign adhesives. The emission of VOC, including formaldehyde, from wood composites has been studied extensively. See, for example, Baumann et al., “Aldehyde Emission from Particleboard and Medium Density Fiberboard Products,” For. Prod. J. 50:75-82, 2000; Henderson, J. T., “Volatile Emissions from the Curing of Phenolic Resins,” Tappi J., 62:9396, 1979; Lambuth, A. L., “Adhesives from Renewable Resources: Historical Perspective and Wood Industry Needs,” Adhesives from Renewable Resources; Hemingway, R. W. Conner, A. H. Branham, S. J., Eds.; American Chemical Society: Washington, D.C., pp 5, 6, 1989.
Second, PF and UF resins are produced from petroleum products. Petroleum reserves are naturally limited. Thus the wood composites industry would benefit greatly from the development of formaldehyde-free adhesives produced from renewable resources.